This invention relates to a magnetic head device used in a magneto-optical recording/reproducing apparatus employing a magneto-optical recording medium, such as a magneto-optical disc. More particularly, it relates to a magnetic head device including a magnetic head configured for being slidingly contacted with a magneto-optical recording medium having information signals recorded thereon.
There has hitherto been employed a magneto-optical disc recording/reproducing apparatus employing a magneto-optical disc having a magneto-optical recording layer formed by a perpendicular recording film on a light-transmitting transparent substrate as a recording medium.
With the magneto-optical disc recording/reproducing apparatus, an optical pickup device for radiating a light beam for illuminating the magneto-optical recording layer is arranged facing the magneto-optical disc on one major surface of the magneto-optical disc rotated by a disc rotation mechanism.
With the magneto-optical disc recording/reproducing apparatus, a magnetic field whose direction is modulated in accordance with recording information signals is applied by a magnetic head device on a magneto-optical recording layer of the rotating magneto-optical disc, at the same time as a light beam outgoing from an optical pickup device is radiated on the magneto-optical recording layer. The portion of the magneto-optical recording layer which has lost its coercivity by being illuminated with the light beam and thereby heated to higher than the Curie temperature is magnetized in accordance with the direction of the magnetic field applied by the magnetic head device. The light beam is relatively moved with rotation of the magneto-optical disc so that the above portion is no longer illuminated with the light beam and hence its temperature becomes lower than the Curie temperature. The information signals are recorded by fixation of the direction of magnetization.
With the conventional magneto-optical disc recording/reproducing apparatus, the magnetic head is caused to face the magneto-optical disc without being contacted therewith during recording of the information signals with a view to prohibiting the magneto-optical disc from becoming damaged by sliding contact with a metal core constituting the magnetic head, such as a ferrite core.
Thus the conventional magnetic head device is provided with an electro-magnetic control mechanism for displacing the magnetic head in following the surface deviations of the magneto-optical disc for holding the magnetic head at a pre-set distance from the magneto-optical disc without being contacted therewith even if surface deviation have been incurred during rotation of the magneto-optical disc due to warping or thickness fluctuations in the disc.
With the magnetic head device provided with the electro-magnetic control mechanism for displacing the magnetic head in following surface deviations of the magneto-optical disc for holding the magnetic head at a pre-set distance from the magneto-optical disc, the electro-magnetic control mechanism needs to be driven by an electric power thus increasing the power consumption. In addition, a detection mechanism for detecting the distance between the magnetic head and the magneto-optical disc is required, thus complicating the mechanism for controlling the magnetic head device. In addition, the recording/reproducing apparatus becomes complex in construction thus rendering it extremely difficult to reduce the size and thickness of the apparatus itself.
Thus a magneto-optical disc recording/reproducing apparatus has been proposed which is provided with a magnetic head device adapted for being slidingly contacted with the magneto-optical disc for recording information signals thereon in place of the magnetic head device adapted for controlling the magnetic head so as to be at a distance from magneto-optical disc.
The magnetic head device employed with this type of the magneto-optical disc recording/reproducing apparatus has a slide contact member adapted for having sliding contact with the major surface of the rotating magneto-optical disc and a magnetic head element mounted on the slide contact member and made up of a magnetic core and a bobbin fitted with a coil. The slide contact member thus carrying the magnetic head element is supported by the distal end of a head supporting arm via a resiliently flexible support. If, when the magneto-optical disc is run in rotation, with the slide contact member being in sliding contact with the magneto-optical disc, the disc is subjected to surface deviations, the resiliently flexible support is resiliently flexed so that the slide contact member perpetually maintains its pre-set sliding attitude so as to be in sliding contact with the magneto-optical disc.
The head supporting arm is formed by a resilient spring plate in order to cause the slide contact member carrying the magnetic head element to be contacted with and displaced from the magneto-optical disc and in order to cause the slider to be slidingly contacted with the magneto-optical disc with a pre-set sliding contact pressure. That is, the head supporting arm is rotated by a rotary member provided on the magneto-optical disc recording/reproducing apparatus for causing the slide contact member to be contacted with and displaced from the magneto-optical disc. When the slide contact member is in sliding contact with the magneto-optical disc, the head supporting arm is resiliently displaced for biasing the slide contact member towards the disc.
The support supporting the slide contact member on the distal end of the head supporting arm for resilient displacement has a pair of supporting arms supporting both opposing sides of the slide contact member. The support supports the slide contact member by these supporting arms so that the slide contact member is resiliently deflected so as to be rotated in a direction perpendicular to the direction of resilient deflection of the head supporting arms about the supporting arms as center of rotation. That is, the support having these supporting arms supports the slide contact member so that the slide contact member performs a wobbling deflecting movement on the major surface of the magneto-optical disc. The head supporting arms are designed to have an elastic force sufficiently smaller than the resiliency of the slider supporting arms in order to permit the slider to be deflected in following the surface deviations of the rotated magneto-optical disc.
Each supporting arm constituting the support for the slider has its distal end secured to the head mounting arm and is mounted via the head mounting arm on a mounting base provided within the magneto-optical recording/reproducing apparatus. Thus the slider supporting arm is supported by the head supporting arm in a cantilevered fashion by being fixed at its proximal end about which it may be resiliently deflected in a direction towards and away from the magneto-optical disc.
With the above-described magnetic head device, in which the slide contact member carrying the magnetic head elements is slidingly contacted with the rotated magneto-optical disc for recording information signals, the head supporting arm supporting the slide contact member is formed by the spring plate, in order to permit the slider to be contacted with and displaced from the magneto-optical disc and in order to permit the rotated magneto-optical disc to be in sliding contact with the disc with a pre-set sliding contact pressure.
On the other hand, the head supporting arm affords the slide contact member with a bias force in order to permit the slide contact member to be slidingly contacted with the rotated magneto-optical disc with a pre-set sliding contact pressure. It is sufficient if the force of bias which biases the slide contact member towards the magneto-optical disc is such a force which causes the slide contact member to be slidingly contacted with the magneto-optical disc with a pre-set sliding contact pressure without the slide contact member being floated significantly from the major surface of the rotating magneto-optical disc. If the force of bias which causes the slide contact member to be slidingly contacted with the magneto-optical disc is excessive, the sliding friction between the slide contact member and the magneto-optical disc is increased thus producing significant wear to the slide contact member and the magneto-optical disc. Thus the head supporting arm is formed by a thin spring plate of a rather small resilient force and insufficient mechanical strength. The slide contact member has its proximal end mounted on the head supporting arm so as to be supported in a cantilevered fashion by the head supporting arm.
If an impact is applied to the above-described magnetic head device, there is readily imposed a load in excess of an elastic limit on the head supporting arm which is formed by a thin spring plate of an insufficient mechanical strength and which is supported in a cantilevered fashion, thus readily deforming the head supporting arm. In particular, if an impact is applied to the slide contact member, there is concentrated a load on the proximal end thereof secured to the head mounting arm, thus producing significant deformation of the proximal portion.
This ready deformation on impact application is similarly produced when the magnetic head device is mounted on the magneto-optical recording/reproducing apparatus. That is, if an impact such as that of inadvertent descent is applied to the magneto-optical recording/reproducing apparatus itself, the impact is transmitted to the magnetic head device thus readily deforming the head supporting arm.
With the magnetic head device, it is necessary to provide a jumper for electrically connecting a coil of the magnetic head element mounted on the slider supported by the distal end of the head supporting arm to an external circuit. Thus, with the conventional magnetic head device, an electrically conductive line of a flexible wiring substrate is extended on the head supporting arm so that the coil of the magnetic head element and the external circuit are electrically connected with each other by this jumper. This leads to an increased number of component parts for electrically connecting the coil and the external circuit. In addition, the wiring connection by a solder is necessary thus raising difficulties in connection with production.